Anticipated Impacts on Veterans Health Care: Veterans served by the VHA suffer both higher prevalence and higher mortality from lung cancer than the general population. The recent National Lung Screening Trial (NLST) demonstrated a 20% reduction in lung cancer mortality and a 7% reduction in all cause mortality with annual chest CT screening among current and former smokers aged 55-74. Accordingly, several new clinical practice guidelines recommend CT screening for middle-aged smokers - a group which would encompass millions of Veterans. CT screening for lung cancer has the exciting potential to reduce lung cancer death, but also the potential for huge costs to the VHA and adverse outcomes for Veterans if not implemented in a thoughtful fashion. The proposed work is of critical importance to our operational partners, the National Program Offices for Oncology and Pulmonology and the National Center for Health Promotion & Disease Prevention, who have been tasked by the Under Secretary for Health with conducting a clinical demonstration project of implementation of lung cancer screening in the VHA. Background: Despite the impressive efficacy of CT screening at reducing lung cancer mortality, CT screening also has downsides. Almost 40% of NLST participants in the CT arm had a pulmonary nodule detected that required further evaluation to rule out cancer - and 95% of those turned out to be false positive findings. Guidelines for pulmonary nodule evaluation are complex, requiring clinicians to choose between CT surveillance, PET scan, transthoracic needle biopsy, bronchoscopic biopsy, and surgical resection; and are not consistently followed either inside the VHA or in the private sector. Meanwhile, patients who require surgical resection have better outcomes if operated on in centers with expertise in thoracic surgery. In light of these factors, guidelines recommend that lung cancer screening be conducted in centers with a comprehensive process for both screening as well as downstream evaluation and treatment of potential cancers. Whether VA providers perceive the evidence for screening as robust and which sites have the local context in place to ensure successful implementation of comprehensive lung cancer screening programs is unknown. Objectives: To meet the needs of our operational partners and following the revised PARIHS framework, we propose to assess the evidence, context, and facilitators relevant to implementation of lung cancer screening programs in the VHA. This will inform selection of sites for implementation of lung cancer screening programs, tailoring of needs-based implementation strategies for these sites, and planning and execution of the clinical demonstration project of lung cancer screening that our operational partners are leading. Methods: Aim 1: We will conduct an online survey of all VAMC pulmonologists to assess perceptions of evidence and local context for implementation of lung cancer screening at their site. Aim 2: We will conduct diagnostic formative evaluations 2 VA sites that have already implemented lung cancer screening programs to inform planning and implementation of the clinical demonstration project, and then conduct a 3rd, implementation-focused formative evaluation at one of the 6 clinical demonstration project sites to assess success of implementation.